Coronary artery disease (CAD) is a national and worldwide epidemic that places the largest clinical and economic burden on the healthcare system of any disease condition. Patients with stable and acute coronary conditions are often treated with percutaneous coronary intervention (PCI), including stenting. Up to 85% of all coronary stents are under-deployed leading to higher target revascularization rates (TVR), in-stent restenosis, in-stent thrombosis, and therefore, higher mortality. Under-deployment is related to several factors, including inaccurate manufacturer ex vivo versus in vivo pressure/diameter compliance relationships, and thus requires further post-dilatation typically with a stiffer, non-compliant balloon. However, post-dilatation balloons still fail to provide adequate expansion because, similar to the stent deployment balloons, they also rely on ex vivo compliance charts to determine in vivo size. Consequently, a tool is needed to provide accurate balloon sizing information to the clinician in real-time during balloon inflation. A novel conductance balloon (CB) catheter system has been developed that functions as a typical post-dilatation catheter, but with additional functionality for accurate measurement and display of real-time balloon size. The CB catheter utilizes a simple physical law (Ohm's Law) to determine the balloon cross-sectional area (CSA)/diameter through electrical voltage measurements made inside the device during inflation. The sizing results are displayed in-real time on a simple bed-side console display to aid the physician during balloon expansion (i.e., similar to current displays that show pressure during inflation). Preliminary results with the CB catheter system on the bench and in vivo in healthy swine showed excellent accuracy (1.4% diameter error), repeatability (1.1% diameter error), and safety. However, additional work is needed to update the console and catheter and further validate the system in atherosclerotic swine (this Phase I application) before translation to the clinic (future Phase II application). Therefore, in this Phae I application, we propose the creation of a clinically-ready CB catheter system and its validation in vivo in atherosclerotic swine. Based on the strong physics foundation of the technology, the excellent preliminary results, and the previously known safety of a related system, the CB catheter system is expected to provide highly accurate and repeatable real-time digital display of balloon size across the entire coronary stent range in any type of diseased vessel condition with virtually no physician training required. After the completion of this Phase I project, we expect a quick and logical translation of the CB catheter system to a Phase II project in man. This project has the ability to impact patients with multiple comorbidities and reach across various NIH Institutes and Centers including the NIDDK, NHLBI, and NINDS.